Ophthalmoscopy - clinical skills PDF

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Summary

Ophthalmoscopy Examining the eye – looking at the external eye, the optic media and the fundus.  Used to detect signs of: o Cataract o Retinoblastoma o Hypertension o Diabetes o Macular disease o Optic nerve inflammationTypes:  Direct – ‘Panoptic’ o View the eye and the fundus directly (actual/re...

Description

Ophthalmoscopy  Examining the eye – looking at the external eye, the optic media and the fundus.  Used to detect signs of: o Cataract o Retinoblastoma o Hypertension o Diabetes o Macular disease o Optic nerve inflammation Types:  Direct – ‘Panoptic’ o View the eye and the fundus directly (actual/real image). o Monocular image – can be used with either eye – good for amblyopic practitioners. o Real (direct) image o Right way up o Small field of view – panoptic enables 25o field-of-view vs. the standard 5o field-of-view with standard direct ophthalmoscope. o Magnification ~15x – panoptic increases mag by 26% over a standard ophthalmoscope and has greater working distance. o Portable o No other equipment needed o No pupil dilation needed usually – east for small undilated pupils. o This is a system of lenses (for focusing) and illumination – adjust the lenses to get clear view. o To view the fundus – use lenses that correct for refractive error (yours and px’s) and viewing distance – use the power wheel and auxiliary lenses.

 Indirect – silt lamp with condensing lens and head mounted. Routine:  Explain to px what you are going to do in lay terms.  Tell px to look at a fixation target.

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Px sits at similar or lower level. No spectacles Turn off room illumination Observer stands on side of examined eye. RE for RE and LE for LE.

1. View the external eye. o Px eyes closed. o Viewing distance 10cm o Using a high-power lens (+10) in addition to your refractive correction – not px. 2. Reduce power slightly to view the iris and the lens. o Observe the red reflex – reflected light from the choroid. o Opacities appear dark against this light. o Adjust brightness – use appropriate aperture size (large to view external eye, small to view macular). o Place your free hand on headrest behind px, on shoulder or preferably or px’s forehead. 3. Start to reduce power of focusing lens (rotate power wheel) and check clarity of media. o Ask px to look up, down, right and left. o Swing 30o up, down, right and left. 4. Continue to reduce power of the focusing lens to focus on the vitreous (e.g. floaters). 5. Continue reducing lens power until fundus is in focus. o ~2cm from the cornea. o Locate the optic disc. o Locate the fovea – macular region lies about 15o temporal to the optic disc, and is along the visual axis. Px needs to look directly into the light.

Features of fovea

 Avascular area – no blood vessels – they arc around this region.  Might see small pin-prick of light – foveal reflex – very central of macula – brighter in younger px’s. Fundus periphery  Px looks up/down/left/right – 8 directions of gaze.  Adjust the viewing angle too.  Examine the retinal background and blood vessel ‘tree’.  Look for normal appearance. Observations of optic disc  Observe the disc colour and shape.  Notice the blood vessels appear from the disc and progress to all regions of the fundus.  Observe the region where the blood vessels originate – optic cup.  Disc is the wide, round region, paler than the surrounding fundus.  Cup is central region from which the blood vessels emerge – often paler than the rest of the disc.  Neural Retinal Rim (NRR) o Pink capillary-rich ring of nerve tissue of the ONH – very important in assessing health of ONH. o Red-free filter may be helpful. o May not be thick all the way around  thick to thin order of inferior/superior/nasal/temporal o Observations  should be smooth, regular and intact 360 degrees. Look for notches (bites and variation in hue. o Compare both eye – rim appearance should be similar.

Cup: Disc ratio

Pallor – describe the colour of the optic cup relative to the surrounding disc. But the pale region does not necessarily coincide with the cup.

Direct ophthalmoscopy Advantages o Evaluation of posterior pole ‘undilated’ o Quick o Portable o Minimal px cooperation o Easy to master and perform o Px comfort Disadvantages o Limited field of view (approx. 5o) o No depth perception (stereopsis) o Refractive error can distort view o Cloudy media can reduce view o Short WD.

Indirect ophthalmoscopy (view SL with condensing lens w the eye and the fundus indirectly – virtual image): SL with condensing lens o Binocular image (BIO) o Back-to-front image o Inverted o Reversed o Large field of view o Condensing lens (Volk) +66D, +78D, +90D  the stronger the power of the condensing lens – the closer it must be to the eye. o Independent of Rx o Magnification approx. 5x -70x o Pupil dilation may be needed Indirect ophthalmoscopy: Head-mounted BIO o Binocular image o Back-to-front image o Inverted o Reversed o Large field of view o Condensing lens +20d o Independent of Rx o Magnification approx. ~2x -5x o Pupil dilation may be needed o Portable Limitations of direct and indirect ophthalmoscopy o Ophthalmoscopy vie can be limited by small pupils o Restricted fundus view o May be necessary to dilate pupil o Large dilated pupil is obtained with the use of eye drops o Pupil dilation – mydriasis  relevant drops are mydriatic or cycloplegic. Features: o Large aperture – for external eyes. o Medium aperture – looking through media to back of eye. o Small aperture – macula – fine detail viewing.

o Shining white light on red object – everything observed except long wavelengths – see it as red. o Green filter blocks long wavelengths and appears black – increasing contrast. Fixation target o Px and practitioner can both see the target. o To check whether the px is using central (foveal) fixation: let the px look directly at the centre of the target and observe whether the fovea is in the centre of the target. o Non-central fixation can explain poor visual acuity in some px. Depth evaluation: Slit beam o No ‘stereoscopic’ (binocular) viewing of fundus so depth is not easy to assess. o Slit aperture in the ophthalmoscope may be helpful to examine contours and assess the depth of findings in fundus. o A slit of light becomes deviated when it illuminates a surface that is not flat. Depth evaluation: focusing o Focusing on fundus features that are elevated or depressed. o More + indicates more anterior or elevated (closer to you) – optic disc. o More – indicates more posterior or depression (further from you). o In general, 1D ~1/3mm i.e. ~3D/mm. o Shallow, smaller cupping is better. o Concealment – more posterior structures are covered by more anterior ones. Depth evaluation: Parallax o Reveals apparent displacement of objects against background if ophthalmoscope is moved laterally.

o Objects in front of P (your point of focus) will produce WITH movement. o Objects behind P will produce AGAINST movement. Optic disc features Pigmentation at the optic disc margins: Choroidal crescent – common form of hyperpigmentation. o Choroid but not retinal pigment epithelium (RPE) extend to the optic nerve head – allows the choroid to be visible as a dark region. Scleral crescent o Neither RPE nor choroid extend to the optic nerve head – sclera is visible as a relatively pale region.     

Asymptomatic – no visual loss. Generally isolated findings Associated with – high myopia (elongated globe) and ‘tilted disc’. ONH margins harder to recognise. No treatment.

Neural Retinal Rim (NRR) Lamina Cribrosa o Visibility should be noted. o The ‘cribriform plate’ is a region of collagenous CT. o Sieve-like – provides support to nerve axons located here. o Commonly visible – more often seen with large C/D ratios. More visible with age and nerve fibre loss (glaucoma). Cilio-retinal Artery o About 1 in 5 people have this – branches from ciliary circulation and supplies the macula and the optic nerve. o Blockage – pale fundus due to lack of blood supply from this artery. Red fundus due to supply from artery.

Myelinated nerve fibres o Nerve fibres with myelination – should be absent from retina. Myelinated region has a corresponding visual field defect (vision us lost in that region). Retinal vessels o Central retinal artery and central retinal vein branch from the ophthalmic artery and come into the eye through the optic nerve head. o Each then branches from the optic nerve head to serve four main quadrants of the retina. o Provide the blood supply for the inner 2/3rd of the retina. o Arteries vs veins  Central retinal artery – usually nasal to vein.  Arteries smaller in diameter.  Colour – arteries light red (more oxygen) and veins dark red.  Cross-over – arteries and veins have crossing points.  Width of artery compared to vein – expressed as a fraction: 3/4, 2/3 or ½  must be measured in the same region for artery and vein.  Uniform calibre (width) of vessels – should be similar before, during and after crossing. Atherosclerosis can affect apparent width. Fundus appearance  More skin pigment = darker fundus appearance.  Tessellated fundus = elongation of the globe along with hypoplasia of the retinal pigment epithelium may expose the underlying choroidal vessels giving rise to a tessellated fundus appearance....